Urine pH reflects the body’s metabolic activity. Its measure allows to make diagnoses and follow-ups of different disorders in an economic way.

The urine sample serves physicians as a sentinel method to assess the health of the kidneys and other areas of the body. Among other parameters that are studied is the  hydrogen potential or pH of the urine.

Since ancient Greece, urine was used as a diagnostic method. Color, turbidity, odor, volume, viscosity, and even sweetness was valued. From the invention of the microscope in the seventeenth century, the urinary sediment began to be studied and it was incorporated as a routine study method of the medical check-up.

At present, the urine test has become an accessible, inexpensive, non-invasive and easy-to-collect study that allows guiding the differential diagnosis of various conditions.  Among the parameters studied in the urinary sample is the pH of the urine.

The normal functions of the kidney are maintained thanks to multiple cellular processes. If any of these functions are disturbed, health may be threatened. We will start with some general concepts to understand the concept that concerns us.

What is urinalysis for?

As we have said, urinalysis is a non-invasive study method that fulfills a multitude of functions in the detection and monitoring of different pathologies:

  • Monitoring the evolution of a known kidney disease.
  • Diagnosis of acute or chronic kidney disease in patients with other suspected symptoms.
  • Finding of renal pathology in a patient with no apparent symptoms.
  • General disease marker.

What parameters of urine are studied?

In a urinalysis, various parameters can be studied, among which are the following:

  • Glomerular filtration rate: Main measure of kidney function.
  • Urinary sediment: Erythrocytes, leukocytes, casts and crystals in urine.
  • Proteinuria: Abnormal elimination of protein in the urine.
  • Urinary ph.
  • Urinary volume alteration: Oliguria, anuria, polyuria.
  • Presence of glucose in urine.
  • Electrolyte abnormalities: Sodium, chloride, potassium, calcium.

What is the pH of urine?

This concept refers to the concentration of hydrogen ions in urine and reflects the degree of acidity of the same. Its normal value is between 4.5 and 8. It is closely related to the pH of the blood.

The complex body mechanism that regulates blood pH is made up of three mechanisms that work simultaneously:

  • The kidneys.
  • Lungs.
  • A chemical buffer system.

The way that the kidneys contribute to the pH balance in the blood is through the elimination in urine, or retention, of acidic or alkaline substances, according to the body’s need. The aim is always to keep the pH of the blood at a healthy value, around 7.4.

Urinary pH can be classified into three grades:

  • Acidic urinary pH when the value is low: less than 5.5.
  • Alkaline urinary pH when it is high: greater than 7.
  • If the pH is 7, it is said to be neutral.

Whenever an altered urinary pH is found, the patient’s blood pH and medical history should be considered, as well as his renal function, the presence or absence of a urinary infection, the contribution of the diet consumed, and so on.

Causes of acidic urine.

There is a long list of causes that generate acidic urine. Among them are the following:

  • Chronic obstructive pulmonary disease or emphysema.
  • Diabetes mellitus.
  • Starvation.
  • Dehydration.
  • Diarrhea.
  • Presence of acid-producing bacteria, such as Escherichia coli.
  • High protein diet.
  • Cranberry juice.
  • Medications.

Causes of alkaline urine.

On the other hand, the possible causes of alkaline urine are the following:

  • Hyperventilation.
  • Vomiting.
  • Renal tubular acidosis.
  • Presence of urease-producing bacteria.
  • Vegetarian diet.
  • Old samples.

What is the ideal urine sample?

The first urine of the morning is the ideal sample for a urine test. It is usually a concentrated sample that guarantees the detection of chemicals and elements that may not be detected in a random sample.

After its collection, it should be delivered promptly for analysis in the laboratory. If delivery is not immediate, it should be refrigerated at 2-8 °C to avoid bacterial growth and metabolism of the sample. In addition, the pH can be altered and give an inaccurate value.

Importance of urine pH measurement.

The study of urine samples is inexpensive and easy to obtain. It allows to assess many of the metabolic functions of the body. For example, it is known that both a low urinary pH and a high urinary pH can promote the formation of kidney stones of different types.

Together with the rest of the urinary parameters, pH is an important element when performing various diagnoses and follow-ups.

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